1. Field of the Invention:
This invention relates to apparatus for applying forces to glass being formed into a continuous sheet of glass while floating on molten metal. This invention is particularly related to glass-engaging rolls employed in the manufacture of flat glass which is thinner than equilibrium glass.
2. Description of the Prior Art:
The following United States patents describe devices and methods of applying forces to glass while the glass is floating on molten metal in order to form continuous sheets of glass that are thinner than the thickness of glass produced when glass is permitted to float on molten metal, such as tin, to an equilibrium thickness.
U.S. Pat. No. 3,083,551 to Pilkington describes the general use of top edge rolls to maintain the width of an advancing body of glass that is undergoing stretching or attenuation forces to produce a continuous ribbon or sheet of glass of desired thickness.
U.S. Pat. No. 3,248,197 to Michalik et al discloses the general use of edge rolls shown as knurled rolls for engaging the marginal edge portion of an advancing body of glass to maintain the width of the glass during its stretching or attenuation toward a desired final thickness.
U.S. Pat. No. 3,353,943 to Loutte illustrates a glass edge-engaging wheel having internal means, including an internal baffle, for maintaining the temperature of such rolls during use in a glass manufacturing operation. The device described by Loutte is a device which engages the glass along its face, rather than about its periphery, although embodiments are described which include a cylindrical projection which does engage the top surface of a body of glass along the periphery of the cylindrical projection.
U.S. Pat. No. 3,709,673 to Bishop describes a fluid-cooled barrel for an edge roll machine along with a fluid-cooled shaft for connection to a hollow edge roll which receives coolant through the shaft during operation.
U.S. Pat. No. 3,929,444 to May et al describes a carriage-mounted edge roll assembly including, in a preferred embodiment as a subcombination, the water-cooled barrel and shaft assembly of Bishop.
The glass-engaging edge rolls described in the above-mentioned patents have been found to be useful for engaging the upper surface of a body of glass floating on molten metal, such as tin, in a glass forming chamber and have been effectively used to provide both tractive and stretching forces to glass to form glass into continuous sheets of desired thickness. Occasionally, problems have been encountered wherein molten glass sticks to an edge roll and consequently is drawn to one side of a forming chamber creating operational difficulties. The sticking occurs when a portion of the edge roller is not cool enough. When the metal of the roll is hot, then glass will stick to the roll. A portion of the roll edge may become hot because of sediment deposits or uneven coolant flow. Increased tonnage of glass production have made the problems of maintaining cool rolls more difficult. There remains a need for an improved edge roll intended to minimize the possibility of glass sticking to the edge roll while permitting the edge roll to be fabricated from conventional materials, such as stainless steel, rather than resorting to materials which are not wet by glass but which are subject to substantial wear when used as glass-contacting materials.